1. Field of the Disclosure
The present invention relates in general to roofing and, in particular, to a system, method and apparatus for increasing the surface solar reflectance of roofing shingles.
2. Related Art
It has been shown that surfaces of man-made structures, such as a roofing covering, cladding, or pavement surface, can absorb significant amounts of solar radiation. This causes the so-called “heat island effect,” where the temperatures in an urban area tend to be several degrees higher than surrounding areas. As a result, significant amounts of solar heat flux can be absorbed due to those surfaces with low solar reflectivity, particularly on hot summer days. This not only increases the demand for indoor cooling energy, but also contributes to smog formation due to higher surface temperatures. Hence, it is beneficial to have a surface with increased solar reflectance to reduce solar heat gain thereby reducing the heat flux entering building envelopes or reducing surface temperatures for lowering smog formation.
This effect is particularly true for mineral-surfaced bitumen roofing products, such as those described in ASTM D225 and D3462. The bitumen or asphalt-based roof coverings are generally constructed from asphalt-saturated roofing felts and surfaced by pigmented color granules, such as those described in U.S. Pat. No. 4,717,614. However, such roofing granules and the resultant roofing membranes or asphalt shingles are known to have low solar reflectivity and hence will absorb solar heat especially through the near infrared range of the solar spectrum. As a result, it is common to measure temperatures as high as 160 to 170° F. on the surfaces of dark roofing shingles on a sunny day with 80° F. ambient temperatures. In recent years, there have been mineral particle surfaced, asphaltic roofing products that are designed to reduce solar heat absorption. This has been achieved by coloring the surface mineral particles with solar reflective colorants. However, the mineral particles typically cover only about 80% to 95% of the shingle surface. The remaining uncovered area of shingles can still absorb significant amounts of solar radiation. As a result, this exposed, highly absorbing asphalt surface can reduce the total solar reflectance by as much as 20%.
Hence, it would be desirable to have a mineral-surfaced roofing product with an exposed asphalt area that can be covered by reflective media that can fit in between the mineral particles. It would also be desirable to have a process wherein the reflective media can be efficiently deposited onto the exposed asphalt area without affecting granule adhesion or the overall aesthetics of the shingles.